With the brisk advance of the semiconductor industry recently, the sizes of semiconductor devices have become smaller and smaller than before in the field of Ultra Large Scale Integrated (ULSI) technologies, in order to achieve high performance integrated circuits or high package density of a wafer. In general, the integrated circuits include more than millions devices in a specific area of a wafer and electrically connecting structure for connecting these devices to perform desired function. The performance of the integrated circuits is related to the performance and reliability of its constituent individual devices. Besides, the innumerable fine peripheral circuits are needed for the integrated circuits in order to drive or control these devices to perform their function. Each device also requires interconnections for exchanging electrical signals from one device to another device. Specifically, multi-level interconnection techniques are widely used for high-density integrated circuits with the decreasing scales of the semiconductor manufacture.
However, due to the limitation of the resolution of the lithography process, the depth of focus can not be controlled precisely and effectively. Thus, the accuracy and resolution of the defined patterns are hardly maintained. And, the procedures to deposit the metal layer and etch the films especially copper also are difficult to control. For overcoming the issues above, the damascene technique used to form the trench connection and the conductive plug on the substrate simultaneously is widely developed, in order to manufacture the multi-interconnections. As well known about the damascene technique, the plug of the damascene is used to electrically connect the substrate and the trench interconnections above the substrate. Accordingly, by widely applying the dual damascene process to the manufacture of submicron very large scale integration circuits, the reliability and yields of the integrated circuits are mainly promoted, and the ability for manufacturing the interconnections is also promoted.
It is noted that two photo masks are usually needed in the process of manufacturing damascene structure for defining respectively the trench pattern and the contact hole pattern onto the substrate. However, with the continuous increasing integration and the decreasing scales of the various devices, the sizes of the dual damascene structures are similarly shrinking. Thus, when the two photomasks are used in the process for forming the damascene structures, the slight inaccuracies cause the misalign between the trench pattern and the contact hole pattern. And the yields and performance of the produced dual damascene are principally decreased. Namely, the resistance between the trench connection and the plug formed in latter steps is increased, and the conductive efficiency among the interconnections is lower.
Besides, in the conventional art, usually the photoresist is formed into the trench structures after defining the trench patterns, in order to prevent the trench structures suffering from etching damage in performing the step to define the contact/via hole pattern. However, that the depth of focus can not be controlled precisely in defining the photoresist pattern causes difficulty to control the contact/via hole pattern especially as their size becomes smaller and smaller. The yields and the efficiency of the dual damascene structures are reduced.